Glow discharge lamp



July 5, GRAY GLOW DISCHARGE LAMP Filed Oct. 1, 1926 (Safe/ebb ran my if M /a Af/arrrey Patented July 5, 1932 UNITED STATES.

FRANK GRAY, OF NEW YORK, N. Y., ASSIGNOR TO BELL TELEPHONE PATENT OFFICE LABORATORIES,

INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF -NE! YORK GLOW msonniwn LAMP Application filed' October 1, 1926. Serial at. 138,831.

This invention relates to a glow; discharge lamp, and more particularly to a lamp in which the discharge is confined to one side of the cathode. It is especially suitable for picture reception and television systems- The general object of this invention is to improve the light emitting qualities of a glow discharge lamp. This object has been attained by confining the glow discharge to one side of the lamp and by causing substantially all of the light produced by the discharge to pass out through'the viewing field from an area as large asthe viewing field.

This application is a continuation in part of a copending application. of Frank Gray, Serial No. 119,550, filed June 30, 1926.

It has previously been proposed to confine the discharge to certain desired portions of the electrodes by covering other portions with insulation. Such a structure is difiicult to manufacture and maintain.

1 According to this invention the glow dis: charge is confined to one side of the cathode by preventing any discharge within the space between the electrodesby-anequivalent insulation between them. Such an equivalent insulation results when two electrodes are positioned at a uniform distance from each other and very close together in a rarified gas. When. the electrodes are so positioned the discharge spreads out and over the'front surface of the cathode and takes the longer path from the anode around to the far side of the cathode, rather than a much short path across the space between the two plates, with the result that the emission of light takes place principally'fromsthe front of the cathode. This.

phenomenon has been-taken advantage of in this invention bypositioning the electrodes,

with a uniform and small separation within a glass bulb containing rarified gas or vapor,

. such as neon or other suitable gas or combination of gases. 1 When the lamp is in operation the light emitted is substantially proportional to the current flowing therethroughg To render the emitted light more unif0rm,

especially at'low intensities, the surface of the .bulbgopposite the light emitting cathode may be frosted.

In picture reception and television systems, the receiving lamp is usually required to emit light in one direction only and the construction employed in this invention meets this condition by causing substantially all of the light to be emitted from one side or surface of the cathode. This invention is particularly applicable as the receiving lamp in the television system, such as is'shown in a copending application of F. Gray, Serial No. 111,731, filed May 26, 1926. With a lamp of this construction used in the receiving device of such a system, the light emitting area is somewhat larger than the viewing field and the image may be viewed without the aid of an optical system andit may be seen through a solid angle of substantially 27l' radians.

A more detailed description of the invention follows and is illustrated in the accompanying drawing.

Fig. -1 is a general view of a glow discharge lamp embodying this invention.

Fig. 2 is a' front view particularly showing the electrodes of the lamp of Fig. 1.

Fig. 3 is a general view of a modified construction of glow discharge lamp also embodying this invention.

Fig. 4 is a front view of the electrodes of the lamp of Fig. 3. I

Fig. '5 is a characteristic curve of the discharge between two parallel plates plotted between sparking voltage and separation between the plates.

The glow discharge lamp shown in Fig.

consists of a bulb 10 containing a rarified gas 0r vapor, a plate anode 11, a plate'cathode 12 and positive and negative lead-in wires 13 and14,'respectively. The electrodes may be made of nickel, tungsten, or othersuitable material and the cathode may be treated with I potassium or other alkaline materials to increase the radiation. The use of a cathode having a polished surface increases the light emissive power of the lamp. Suitable spac-' ing members 15 of insulating material are employed to hold the electrodes in close parallel relationship. The electrodes may be circular or: rectangular or. any other desired shape and in the preferredform the anode is ;-.made slightly larger'than the cathode "as is shown more plainly in Fig. 2. The front side 16 of the bulb may be frosted to cause a particularly uniform emission of light over a lar e area.

modified arrangement of this invention is shownin Figs. 3 and 4. The general construction is similar to that shown in Figs 1 and 2 with the exception that the anode 1ncludes an open grid-like member 17 placed 1n front of thecathode in addition to the plate .anode-ll positioned very close to the rear side of the cathode. The plate anode 11 pre vents discharge from the rear side of the cathode in the same'manner as in the construction shown in Fig. 1. The grid-like anode 17 positioned in front of the cathode is corrstructed in the form ofan open mesh screen with large openings so that it forms substantially no obstruction to the passage of light as more clearly shown in Fig. 4. This gridlike portion 17 of the anode is positioned parallel to and in front of the cathode 12 at a substantially greater distance from it than the plate portion 11, and preferably at the minimum sparking distance for the gas ressure in the tube. The purpose of the grid 17 rily, the lamp contained rarefied neon gas and,

is to facilitate the distribution of the glow over the front surface of the cathode 12 particularly when the lamp is operated at'very low current values.

Curve C of Fig. 5 is a typical curve show ing the relationship between the sparking voltage and the separation between paralle plate electrodes at a given gas pressure. This curve shows that as the plates are moved closer together for a certain distance the voltage to produce a discharge directly between the plates becomes less and reaches a minimum sparking distance before they are in contact with each other. If the plates are moved still closer together but not into contact with each other, the voltage required to produce a discharge directly between the plates rapidly increases, and rather than pass across the region between the plates the discharge takes place around the edges of the cathode and over its outer surface. If the plate electrodes are fixed close together and the gas pressure varied the relation between voltage and gas pressure would be quite similar to that shown by the curve C in Fig. 5.

This is substantially in accordance with.

Paschens law that the discharge potential depends only upon the product of the gas pressure and the discharge length.

a In a particular arrangement of a glow discharge lamp which operated satisfactothe plate electrodes were approximately 1 long and 1" wide and positioned face to face parallel to each other with a separation of about of an inch. The pressure of the neon gas was between 2 and 5 millimeters of mercury. In the practical manufacture of these lamps the desired characteristicscan be obtained by using two electrodes having a uniform and fixed separation and varying the pressure of the gas.

The electrodes may be flat, cylindrical,

spherical or any other desired shape, but

should be so positioned with reference to each other, in accordance with the principles set forth above, that tlie low discharge is confined to the viewingfitfie (1.

While this invention has been described as particularly applicable to picture transmission and television systems, it is also applicable to other purposes in which similar requirements are present.

The invention disclosed herein is obviously susceptible to'various modifications and adaptations, without departing from the scope and spirit of the invention, and it is not intended to limit the invention to the specific structures herein shown and described, except as defined by the appended claims. I

-. What is claimed is:

1. A glow discharge lamp having a metallic cathode, an anode member, a member positioned parallel to said cathode, and spaced therefrom by a. distance less than the mini- 'mum sparking distance, whereby said cathmember cathode and an anode, said anode comprising a member substantially the same area and size as the said cathode and positioned parallel to and very close to'the rear side of said. cathode well within the minimum sparking distance and an open member positioned parallel to and'm front of said cathode at a distance equal to at least the minimum sparking distance.

4. In a glow discharge lamp, a plate-like cathode member, a plate-like anode member positioned parallel to and very close to the rear side ofsaid cathode member, and an open grid-like anode member positioned in grid-like front of the plate-like cathode member and electrically connected to said plate-like anode member.

5. A glow discharge lamp including a plate-like cathode member, a plate-like anode member positioned parallel to and very close to the rear side of said cathode member, and another anode member positioned in front of the said cathode member and electrically connected to said plate-like anode member.

6. A glow discharge lamp including a plate-like cathode member, a plate-like anode member positioned parallel to and very close to the rear side of said cathode member, and another anode member positioned in front of said cathode member, all parts of said member, said anode member having a plate-- like portion positioned parallel to and very close to the rear side of said cathode member and another portion positioned on the other side of an extended imaginary plane through said cathode and in front of an imaginary plane extending parallel to and in front of said cathode member at a distance at least equal to the minimum sparking distance, said portions being electrically connected.

In witness whereof, I hereunto subscribe.

my name this 28th day of September,;A. D.

FRANK GRAY. 

